The present invention relates to a method of and apparatus for ejecting material from a liquid. More particularly, the method and apparatus employed may be generally of the type described in WO-A-93-11866, PCT/GB95/01215 and WO-A-94-18011, the disclosure of which is incorporated by reference. In the methods described in these patent applications an agglomeration or concentration of particles is achieved at an ejection location and from the ejection location particles are then ejected onto a substrate, eg. for printing purposes. In the case of an array printer, plural cells may be arranged in one or more rows. In other types of printing apparatus, in which charged liquid droplets are jetted onto a substrate, such as shown in JP-A-05 116 322, U.S. Pat. Nos. 3,060,429 & 3,887,928, additional electrodes may be provided for guiding the charged droplets to a charged substrate.
It is thus known in the art to generate and eject particles by use of electrostatic fields, but problems exist with this type of ejection, such as (a) controlling the direction of movement of ejected droplets or particles, which depends upon close control of the electrostatic field in the vicinity of the ejection electrode, (b) the difficulty of switching and the remote location of electrical earthing, (c) the dependence of ejection on the gap between the ejection electrode and substrate, and (d) the attraction of airborne particles into the ejector during the application of the electrostatic field.